This is a little bit of selfishness on Usagi’s part, which is realistic- she’s a teenage girl, not an endless font of sainthood.
But it’s also one of the good things about Usagi- she sees exceptional women, and rather than being resentful, she admires them and wants to learn from them. All the others look at Ami and all they can do is resent her. But Usagi sees her intelligence and wants to be her friend and learn from her. She doesn’t feel competitive, she admires Ami for who she is and wants to be like her. She sees other women as allies, not enemies, from the beginning.
I think the “women are mysterious” thing can also come from:
1) Women actually being quite clear, but not telling men what they want to hear. ”She said she doesn’t want to talk to me? So many mixed messages and confusing signals!”
2) Women not having cheat codes. ”I tried being nice, and she didn’t have sex with me. I tried being an asshole, and she didn’t have sex with me. Come on, there’s got to be some kind of solution to this puzzle!”
3) Women not being a hive mind. ”First a woman told me that she likes guys with big muscles. Then the very next day a woman told me she thinks muscles aren’t attractive at all. Make up your mind, women!”
4) An individual woman doing something confusing, and instead of asking “why is she doing this now?” men ask “why do women always do this?”